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PhD thesis

Origin of biogenic selenium nanoparticles determines their fate in the environment

PhD student:

Sarah Fischer

Supervisor:

Prof. Dr. Thorsten Stumpf, Dr. Rohan Jain, Dr. Norbert Jordan

Division:

Surface processes

Period:

09/2013 –10/2017 (07/2014 – 05/2016 parental leave)

Motivation:

Selenium is toxic and thus its fate in the environment has to be ascertained. The bio-transformation of Se oxyanions by microorganisms will affect its (bio)availability in the environment. The microorganisms are known to reduce Se oxyanions to biological Se(0) nanoparticles (BioSe-Nanospheres) or biological Se(0) nanorods (BioSe-Nanorods) under mesophilic (30 °C) and thermophilic (55 °C) conditions, respectively. Though both types exhibit a coating of extracellular polymeric substances, their colloidal properties differs, leading to a different mobility in environmental waters [1]. Consequently, understanding the underlying mechanisms of the formation of amorphous BioSe-Nanospheres and trigonal BioSe-Nanorods is essential to understand the fate of selenium in the environment. One such underlying cause can be the microorganisms reducing the Se oxyanions. However, no such study has ever investigated this hypothesis.

Figure 1 and 2: Purified selenium nanoparticles

Objectives:

The aim of this Ph.D. work is to establish a system where the role of microorganisms in the formation of BioSe-Nanospheres or BioSe-Nanorods can be studied. Further, the exact reason for presence or absence of transformation from BioSe-Nanospheres to BioSe-Nanorods will be investigated.

Additionally, the interaction of a Bacillus isolate from the uranium mining waste pile Haberland (Saxony) with selenite will be studied.